Cummins ISX Delete problems

I just bought a 2013 Pete with a cummins ISX engine that has supposedly been deleted. The one thing i noticed is the def fuel gauge always registers empty and i noticed the egr valve computer thing is disconnected as well. I am having a few issues though, first of all the fan wants to run almost all the time above 140 degrees, my mechanic said when they disconnected the exhaust temp sensor the fan started working properly then. So they replaced that sensor but the truck was still throwing a code for exhaust temp sensor but then it went way and now its saying fan clutch driver.
If the truck has had a delete done wouldn't the exhaust temp sensor have been disconnected possibly or is that still working?
Also any ideas on why the fan is coming on?